The purpose of this grant is to provide a computer-based system, using local area network technology, for performing research related to mapping the electrical activation pattern of the heart. Current trends in computing and communications technology can be used to both reduce overall cost and increase the quality of this research, increasing scientific productivity. The goals of the research being pursued by these investigators, individually and in collaboration, is a deeper understanding of the nature of cardiac electrophysiology and metabolism, especially those phenomena associated with sudden cardiac death. Active areas of study include cardiac and body surface mapping during arrhythmias and normal sinus rhythm; simulation of the spread of electrical activity and the interaction of fields with electrodes: the correlation of electrical data with other cardiac variables, especially metabolic; quantitative characterization of cardiac electrograms; and the elucidation of the mechanisms of fibrillation and defibrillation. Despite the apparent diversity, each of these areas shares requirements for certain expensive resources, such as graphics devices, data storage, and software development and maintenance. In order to provide each investigator with adequate computational facilities while avoiding duplication of instruments and program development, we propose the installation of a network of scientific workstations. Such a network takes advantage of price-performance curves in computing technology but gives each investigator local control of his or her own facilities. The shared resources will be managed by the system software and hardware; internode communication will be provided without special user procedures. The usefulness of these resources will be enhanced by the similar computing requirements and commonality of data among the investigators. In addition, the proposed approach to providing computing facilities will allow future improvements and expansions to be made gracefully, without the high costs associated with the purchase of superminicomputers or similar computing equipment. Thus this research effort will be able to exploit technological advances as they become available. Finally, the presence of a sophisticated network will allow the recruitment of talented computer and engineering professionals to further enhance the research capabilities in these areas. This approach is an innovative solution to the problem of providing an appropriate computing environment for small and moderate-sized laboratories that have significant computing and data processing requirements.